Numerous applications require the use of special sealing devices which are composed of low coefficient of friction materials but at the same time are capable of effectively sealing against the flow of fluid between relatively moving parts. Representative of such sealing devices is SPECTRASEAL.TM., manufactured and sold by Microdot/Polydyne of Denver, Colo. The SPECTRASEAL.TM. is capable of being used in static, reciprocating and rotary applications and is generally in the form of a flexible ring having a generally channel-shaped cross-sectional configuration into which is inserted a spring to exert a spreading force against the sidewalls of the ring whereby to force the sidewalls into sealing engagement with the confronting surfaces of the parts to be sealed. The sealing device is composed of various blends of polytetrafluoroethylene together with other inert plastics and is used in combination with a metal spring element of stainless steel or other metal alloy or may be employed in combination with a variety of elastomeric O-springs selected for particular applications. The particular blend of materials selected for given applications may be varied, for example, to withstand extremely broad ranges in temperature and pressure. However, it has been found that certain high temperature or pressure conditions exceed the endurance capacity of such sealing devices. In other words, the properties of the sealing material become adversely affected by extremely high pressure and temperature conditions so that, at least temporarily, the material tends to become misshapen and incapable of maintaining the necessary sealing contact with the relatively moving parts.
It has been heretofore proposed to employ rigid springs which nest into the spring cavity of the sealing device and which will operate both to support the seal and to force the sidewalls of the seal outwardly so as to maintain their sealing contact under extremely high pressure and temperature conditions. Another approach has been to employ oval-shaped inserts in bidirectional types of seals of the type which are joined together at their static lips. These and other types of insert devices have not proven to be entirely satisfactory from the standpoint of potential seal spring damage at their contacts with the internal spring members of the existing sealing device as well as extrusion failure along the sealing surfaces.